1. Field of the Invention
The present invention generally relates to a method and apparatus for removing an adhesively attached heatsink from an electronic module or package.
2. Description of the Prior Art
Heat which is generated by electronic devices during the course of normal operation is typically dissipated into the ambient air before excessive levels can build and cause damage. More sophisticated packaged electronic devices typically comprise several chips in a single package. In this case, a fan or other means must be used to force air over the package to enhance cooling. The trend to compress more chips in a smaller space has lead to the development of multi-layered ceramic module technology which can incorporate numerous heat generating integrated circuit chips in a very confined sealed module. Consequently, these types of modules have particularly challenging cooling needs.
Multi-layered modules are typically mounted to a support card with a plurality of solder ball connections using surface mount array technology. Hence, these modules are sometimes referred to as solder ball connection (SBC) modules. Heat dissipation by conventional convection methods alone has proven inadequate for cooling electronic modules or packages (e.g., SBC modules, etc.) that have a plurality of chips arranged in rows and columns. Typically, the electronic module or package is sealed by a cap which protects the chips but seals in heat. To remedy this, a heat exchanger or heatsink device must be placed in thermal contact with the cap to conduct heat away from the electronic module or package and thereby facilitate cooling.
U.S. Pat. No. 4,854,377 to Komoto et al. discloses a heatsink attached with an epoxy adhesive to a low density integrated circuit package containing several chips. Heat generated by the chips during operation is conducted through the epoxy and is carried away from the module by cooling fluid within the heatsink and thereafter conducted into the ambient air. Epoxy attachment methods have proven superior to many other methods since it assures that the maximum surface areas of the module and the heat sink are in contact for maximum heat exchange.
Epoxy adhesives are substantially a permanent type of attachment method. This presents problems if for any reason a heatsink needs to be removed, such as, for example, when an electronic module or package needs to be repaired or modified, or if the heatsink has simply been initially misplaced on the module or package and needs to be repositioned. Prior art brute force removal methods entail torquing the heatsink with vice-grips while trying to hold the electronic module or package steady. Brute force methods, although sometimes successful, transmit a great deal of stress to the connection joints (e.g., solder balls, etc.) as well as the card. This harmful stress substantially decreases electronic module or package life expectancy and often causes immediate failure.
U.S. Pat. No. 4,381,032 to Cutchaw addresses the problem of removably attaching a heatsink to an electronic module or package by using screws to secure the edges of the two components together. The surface areas of the heatsink and module are not in direct contact, but rather, each chip in the top layer of the module has biased thereto a spring loaded piston which is thermally connected with the heatsink.
U.S. Pat. No. 5,089,936 to Kojima et al. provides a somewhat simplified method for removably attaching a heatsink to an electronic module wherein a heatsink is biased to the sealing cap of the module by a downwardly pressing spring clip. The spring clip and the heatsink are easily removed by loosening two screws securing the spring to jigs attached to the module housing. Although convenient for removal, this attachment method is far less efficient for heat transfer than epoxy attachment methods. The spring clip only applies pressure to the center of the heatsink and therefore the outer surface areas of the module and heatsink will not remain in perfect thermal contact throughout the entire operating and heating cycles of the module.